This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-015968, filed Jan. 24, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to the improvement of a measuring distance device used in a camera or the like and, in particular, to the improvement of a measuring distance device of a hybrid type or a combination type.
2. Description of Related Art
Auto-Focus (AF) techniques which are employed by AF cameras are roughly classified into AF techniques of a passive type using an image to be photographed and AF techniques of an active type using a measuring distance light projected from a camera. However, since these AF techniques have drawbacks based on their respective principles, in order to overcome these drawbacks, AF techniques of a hybrid type (to be referred to as xe2x80x9chybrid AFxe2x80x9d hereinafter) are proposed.
In recent years, an AF in which two measuring distance schemes of a passive type and an active type are switched depending on states has been proposed.
However, various devices are required to rationally selectively use the two measuring distance schemes at a high speed. For example, in Jpn. Pat. Appln. KOKAI Publication No. 8-334678, the following switching scheme is proposed. That is, a passive AF operation is performed, and when the passive AF operation is finished within a predetermined period of time, an AF operation is performed on the basis of the result of the passive AF operation. When the integration process of the passive AF operation is performed for a long period of time, the passive AF operation is switched to an active AF operation.
However, with respect to a camera having the hybrid AF function, only a switching operation of the measuring distance schemes is described, and a switching operation of image signals used in a measuring distance operation is not described.
Even in a camera having the hybrid AF function, a sensor array in which a large number of photoelectric sensors are generally arranged is used to detect image signals. However, when all sensor outputs are used, a long time is taken to perform A/D conversion related to reading of information from these sensors. For this reason, a time lag between a measuring distance state and a photographing state becomes disadvantageously long.
In use of the hybrid AF function, when a measuring distance range is set in the same effective area in an active mode and a passive mode, an effective measuring distance range used in the active mode is limited. However, an ineffective integration process and an ineffective reading operation are performed to cause a further elongation of the time lag and a deterioration in measuring distance accuracy.
Furthermore, a signal of an unnecessary sensor array area is unexpectedly referred to in a measuring distance operation, so that an erroneous measuring distance operation may occur.
The present invention has been made in consideration of the drawbacks and the problems introduced above, and has as its object to provide a measuring distance device which can perform an accurate high-speed process for a hybrid AF camera.
In order to solve the above problems and achieve the above object, a measuring distance device for a hybrid camera according to the present invention is characterized in that in a switching operation between an active AF operation, a limitation on use of an area which is xe2x80x9carea selectionxe2x80x9d of a sensor is performed to optimize a working sensor area. A time lag or the like is shortened without increasing a read area, and an influence on harmful light is minimized as much as possible.
For this purpose, the following means are employed. For example, according to a first aspect of the present invention, there is provided a measuring distance device including:
a sensor array which detects an image signal related to an object to be photographed in a finder screen;
a projection unit which projects a signal light on the object;
a selection unit which selects a detection area for the image signal of the sensor array;
a change unit (control unit) which makes a detection area selected by the selection unit when projection of the signal light is performed by the projection unit different from a detection area selected by the selection unit when projection of the signal light is not performed by the projection unit; and
a focus adjustment unit which performs focus adjustment on the basis of an image signal output in the detection area of the sensor array selected by the selection unit.
According to a second aspect of the present invention, there is provided a measuring distance device including:
a sensor array which detects an image signal related to an object to be photographed in a finder screen;
a first projection unit which projects a first signal light for a measuring distance operation on the object;
a second projection unit which projects a second signal light for a measuring distance operation on the object;
a first measuring distance unit which performs a measuring distance operation on the basis of an image signal output from the sensor array without projection of the signal lights for a measuring distance operation by the first and second projection units;
a second measuring distance unit which performs a measuring distance operation on the basis of an image signal output from the sensor array with projection of the signal light for a measuring distance operation by the first projection unit;
a third measuring distance unit which performs a measuring distance operation on the basis of an image signal output from the sensor array with projection of the signal light for a measuring distance operation by the second projection unit;
a selection unit which selects any one of the first to third measuring distance units;
a change unit (control unit) which changes detection areas for the image signal by the sensor array depending on a selection result of the selection unit; and
a focus adjustment unit which performs focus adjustment on the basis of an image signal output in the detection area of the sensor array selected by the selection unit.
According to a third aspect of the present invention, there is provided a measuring distance device including:
a sensor array which detects an image signal related to an object to be photographed in a finder screen;
an integration control unit which integrates the image signal detected by the sensor array;
a first projection unit which projects a first signal light for a measuring distance operation on the object;
a second projection unit which projects a second signal light for a measuring distance operation on the object;
a selection unit which selects a detection area for the image signal detected by the sensor array;
a first control unit which determines whether, depending on an integration voltage of the integration control unit when projection of light for a pre-measuring distance operation is performed by the first projection unit, an original measuring distance operation is performed by using the first projection unit or an original measuring distance operation is performed by using the second projection unit;
a second control unit which changes detection areas selected by the selection unit depending on a determination result of the first control unit; and
a focus adjustment unit which performs focus adjustment on the basis of an image signal output in the detection area of the sensor array selected by the selection unit.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.